Important: The problem may or may not turn ON the Malfunction Indicator Lamp (MIL), or store a DTC. Do not use the Diagnostic Trouble Code (DTC) tables for intermittent problems. The fault must be present in order to locate the problem.
Most intermittent problems are caused by malfunctioning electrical connections or wiring. Perform a careful visual/physical check. Check for the following conditions:
| • | Poor mating of the connector halves or a terminal not fully seated in the connector (backed out) |
| • | An improperly formed or damaged terminal |
| • | All connector terminals in the problem circuit should be carefully checked for the proper contact tension. |
| • | Poor terminal to wire connection. This requires removing the terminal from the connector body in order to perform the inspection. |
The vehicle may be driven with a J 39200 Digital Multimeter connected to a suspected circuit. When a malfunction occurs, an abnormal voltage is a good indication that there is a fault in the circuit being monitored.
A scan tool can be used in order to help detect intermittent conditions. The scan tool has several features that you can use in order to locate an intermittent condition.
The Snapshot feature can be triggered in order to capture and store the engine parameters within the scan tool when the malfunction occurs. The scan tool stores this data for further reference in order to find the malfunction.
Using a scan tool's Freeze Frame buffer can also aid in locating an intermittent condition. Review and record the information in the freeze frame that is associated with the intermittent DTC being diagnosed. The vehicle can be driven within the conditions that were present when the DTC originally set.
To check the loss of DTC memory, disconnect the TP sensor and idle the engine until the MIL (Check Engine) comes ON. DTC P0122 should be stored and kept in memory when the ignition is turned OFF. If the DTC does not store in the memory, this indicates that the PCM is malfunctioning. When this test is completed, make sure that you clear the DTC P0122 from memory.
An intermittent MIL (Check Engine) with no stored DTC may be caused by the following conditions:
| • | The ignition coil shorted to ground and arcing at the ignition wires or plugs |
| • | The MIL (Check Engine) wire to PCM is shorted to ground. |
| • | Poor PCM grounds. Go to the PCM wiring diagrams. |
If the intermittent condition exists as a start followed by a stall, check for any DTC(s) that relate to the vehicle theft deterrent system.
Check for an electrical system interference that is caused by a defective relay, a PCM driven solenoid, or a switch. These conditions can cause a sharp electrical surge. Normally, the problem will occur when the malfunctioning component is operated.
Check for an improper installation of electrical options such as lights, cellular phones, etc.
Make sure that all of the Ignition Control Module (ICM) wiring is kept away from the generator. Check all of the wires from the PCM to the ignition control module for poor connections.
Check for an open diode across the A/C compressor clutch. Then, check for other open diodes. Go to the wiring diagrams in Electrical Diagnosis.
